(n) Woman who invites herself into your bed, when morning comes does not leave, does not acknowledge subtle hints to leave, makes herself at home. (Editors Note; Sleepers natural evolutionary path is into Bunny Boilers; when one is encountered it is advisable to cease and desist any and all communication while still possible before life and family jewels are still entact)
"Dirk, where are you? Your late, your going to miss the game"
"Sorry, I am having trouble getting this 'Sleeper' out of my house"
Antiques or jewelry items that have been stolen and hidden away. Chiefly of British usage, a sleeper is an item of antiquity, generally of known provenance, stolen and cached, sometimes for years, until it can be sold to a private buyer or exchanged.
"A sleeper is an item that has been deliberately hidden, usually because it is hot." Lovejoy, "To Sleep No More," 1987.